To report bugs, we use Launchpad as our bug tracker so that’s always the best way. Details on reporting bugs can be found at https://phab.lubuntu.me/w/bugs/.
Issues where you need a support type fix, should be posted in the Lubuntu Support of this forum just like you’ve done now. If you look where users have reported issues in support (not with the intention of reporting a bug), and its deemed to be a bug, you’ll often note someone adds a launchpad bug report ID where the issue has been reported so it can be tracked.
If the bug is a feature request then the Development section of this forum makes the most sense to me. The about can be found here. Feature requests may also end up being tracked on launchpad too.
If the issues are design decisions we’ve made; as we’re unlikely to change an existing release, the development section would make sense (we’re mostly working on the next release, and don’t forget the freezes).
If you’re still unsure, I’d post in what you consider the best area, and we’ll move it, or re-direct you if required.